Generally, an ultrasonic concentration meter is a measuring instrument which measures the concentration of various kinds of suspended solids, in real time, either which flow along with a fluid through a pipe or which settles in many types of waterworks plants, such as a water purification plant, a water treatment plant, or a sewage treatment plant.
FIG. 1 is a diagram illustrating the structure of an ultrasonic concentration meter inserted in a pipe according to a conventional art.
As illustrated in FIG. 1, a conventional ultrasonic concentration meter 10 is configured such that an ultrasonic sensor for measuring a concentration is inserted in a pipe 1, an ultrasonic signal radiated from an ultrasonic transmission sensor 11 attenuates by being scattered or absorbed by impurities, foreign substances, suspended solids, etc. contained in a fluid (sample solution) while passing through the fluid, and then reaches an ultrasonic reception sensor 12, and a concentration of a substance in the fluid is measured according to the intensity of the received ultrasonic signal.
The conventional ultrasonic concentration meter 10 has a problem that, when removing the ultrasonic transmission sensor 11 and the ultrasonic reception sensor 12 from the ultrasonic concentration meter 10 for the purpose of maintenance (i.e. replacement or cleaning), the stream of the fluid is adjusted to bypass the ultrasonic concentration meter 10 by closing valves installed at an inlet and an outlet of the ultrasonic concentration meter 10, respectively and opening a bypass valve, and then replacement of the sensors can be carried out thereafter.
Accordingly, the conventional ultrasonic concentration meter 10 needs to be additionally equipped with a bypass pipeline and a bypass valve, which increases installation cost and imposes a limitation on the size of an installation space.
Furthermore, since the entire surfaces of the ultrasonic transmission sensor 11 and the ultrasonic reception sensor 12 are constantly in contact with the fluid which is flowing through the inside of the ultrasonic concentration meter, sludge is likely to stick to the surfaces of the ultrasonic transmission sensor 11 and the ultrasonic reception sensor 12 depending on kinds and characteristics of the suspended solids contained in the fluid when the fluid is maintained at a low velocity for a long period of time or when the concentration of the suspended solids in the fluid is high, attenuating the sensitivity of the sensors. For this reason, the conventional ultrasonic concentration meter has a problem that the sensors need to be periodically cleaned.
That is, since the fluid, a measurement subject, contains various kinds of pollutants and suspended solids which are targets for concentration measurement, the likelihood that the ultrasonic transmission sensor 11 and the ultrasonic reception sensor 12 are broken down is likely to increase.